﻿////
Copyright 2019, 2022 Peter Dimov
Distributed under the Boost Software License, Version 1.0.
http://www.boost.org/LICENSE_1_0.txt
////

[#description]
# Description
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The header `<boost/throw_exception.hpp>` provides a common Boost infrastructure
for throwing exceptions, in the form of a function `boost::throw_exception`
and a macro `BOOST_THROW_EXCEPTION`.

`boost::throw_exception(x);` is a replacement for `throw x;` that both
degrades gracefully when exception handling support is not available, and
integrates the thrown exception into facilities provided by
link:../../../exception/index.html[Boost.Exception], such as automatically
providing a base class of type `boost::exception` and support for
`boost::exception_ptr`.

When exception handling is not available, the function is only declared, but
not defined. This allows users to provide their own definition.

An overload for `boost::throw_exception` that takes a
link:../../../assert/doc/html/assert.html#source_location_support[`boost::source_location`]
is provided. It records the supplied source location into the `boost::exception`
base class, from where it can later be retrieved when the exception is caught.
link:../../../exception/doc/diagnostic_information.html[`boost::diagnostic_information`]
automatically displays the stored source location.

The macro `BOOST_THROW_EXCEPTION(x)` expands to
`::boost::throw_exception(x, BOOST_CURRENT_LOCATION)`, passing the current source
location.

When integration with Boost.Exception and `boost::exception_ptr` is not needed,
the function `boost::throw_with_location` can be used instead. It also throws
a user-provided exception, associating it with a supplied or inferred source
location, but does not supply the `boost::exception` base class and does not
enable `boost::exception_ptr` support.

The source location of the exception thrown by `boost::throw_with_location`
can be retrieved, after `catch(std::exception const & x)`, by using
`boost::get_throw_location(x)`.

`boost::get_throw_location` also works for exceptions thrown by the two argument
overload of `boost::throw_exception`, or by `BOOST_THROW_EXCEPTION`; in this case
it returns the source location stored in the `boost::exception` base class.
